Technical Field
The present invention relates to a water-repellent antifouling coating composition comprising polyorganosilazane as a main component.
Background Art
As a ship used on the ocean always contacts with sea water, the surface of the ship is corroded and marine organisms such as algae and shellfishes attach to it. To prevent such corrosion and fouling, antifouling coating on the surface have been generally applied. For the antifouling coating, coating compositions containing organotin compounds have been used.
However, these organotin compounds are suspected as endocrine disrupters and the use of it has been strictly limited. Therefore, alternative antifouling coating composition has been developed.
Antifouling coating compositions currently being considered can be roughly classified into the followings: (a) a coating composition comprising insoluble resin as a main component and an antifoulant, (b) a coating composition comprising soluble resin or hydrolysable resin as a main component and an antifoulant, and (c) a coating composition type comprising fouling stripping type low-modulus resin as a main component not containing an antifoulant.
On the other hand, an antifouling coating composition desirably satisfies the followings: (1) preparing non-solvent composition to prevent the coating layer from releasing residual organic solvent, (2) not using hazardous or suspected hazardous antifoulant, (3) obtaining coating having sufficient characteristic by one painting, unnecessary to be repeatedly applied, to reduce manufacturing cost at painting, (4) being hardly corroded due to dipping in sea water to prevent further anticorrosion treatment, and (5) being high transparency and not spoiling the external appearance such as designs formed on the undercoating layer.
To meet such needs, various coating compositions are considered. For example, a coating composition comprising polysilazane, polysiloxane, and curing catalyst is disclosed in Patent Document 1. However, according to inventors of the present invention, the composition disclosed in the literature contains curing catalyst and the composition is cured by a condensation reaction of the silanol group. Accordingly, defects such as crack are generated when thick cured layer are formed. There was room for improvement.